Realizations of folded magnet AC motors

Abstract

A rotor assembly for an internal permanent magnet rotor comprises a plurality of interior laminations stacked to form a substantially continuous internal core and a plurality of external laminations stacked to form a substantially continuous external core. A plurality of permanent magnets are positioned between the internal and external cores and folded in the radial plane so as to form a substantially W-shaped arrangement. The magnets may be placed in slots formed through the stacked laminations between the internal and external core sections or the internal and external core sections may be formed as two separate units with the magnets sandwiched therebetween. The core laminations may be strengthened by using nonmagnetic inserts in selected positions which can be welded to the magnetic portions of the laminations. The outer core portion, when separate from the inner core portion, may be held against the inner core portion by bolts through the outer core portion or by a sleeve around the rotor assembly.

What is claimed is: 
     
       1. An interior permanent magnet motor having a stator and a rotor, and a plurality of permanent magnets mounted within the rotor for establishing a preselected number of magnetic poles, each of the magnetic poles being defined by a preselected number of the permanent magnets arranged in a predetermined orientation and relationship with respect to others of the permanent magnets, each of the magnetic poles encompassing a preselected sector of the rotor with edges of each sector lying on a radius line of the rotor, each of the magnetic poles comprising: first and second permanent magnets mounted within a rotor sector adjacent a respective radius line on opposite circumferential ends of the sector, each of said first and second permanent magnets having a magnetic north pole and a magnetic south pole, said first and second permanent magnets being oriented such that said magnetic poles lie in a plane parallel to the respective radius line; and   at least a third and a fourth permanent magnet mounted within said rotor sector, each of said third and fourth permanent magnets being angularly oriented one toward the other such that a radially inner edge lies adjacent a respective one of the first and second permanent magnets and their radially outer edges are adjacent, the north and south polar faces of the magnets being commonly oriented to generate a net magnetic pole in a direction to establish a predetermined magnetic pole in the sector.   
     
     
       2. The motor of claim 1 wherein each of said magnets is positioned in a respective slot extending axially through the rotor, said magnets being held in position in said slots by a relatively rigid potting compound in said slots. 
     
     
       3. The motor of claim 2 wherein a plurality of apertures are formed in an axial direction through the rotor adjacent at least some of the magnets, said potting compound extending through each of the apertures. 
     
     
       4. The motor of claim 3 wherein at least the apertures on the radially outer side of the magnets are coupled to the magnet slots by passages extending therebetween. 
     
     
       5. The motor of claim 1 including a flat spring positioned in each of said slots, respectively, between a surface of a respective one of said magnets located in said slot and an adjacent inner surface of said slot, for compressively holding said magnets in said slots. 
     
     
       6. The motor of claim 5 wherein said flat spring comprises a brass sheet formed as a wavy spring. 
     
     
       7. The motor of claim 6 wherein said brass sheet is at about liquid nitrogen temperature and flattened to facilitate installation in said rotor. 
     
     
       8. The motor of claim 1 wherein each of said magnets abuts an adjacent one of said magnets along at least one axial contact line, said rotor comprising a radially inner portion coupled to a shaft of the motor and a radially outer portion, said magnets being positioned between said inner and outer portions with said slots being defined by spaces between said radially inner and outer portions. 
     
     
       9. The motor of claim 8 wherein said radially outer portion comprises a plurality of separate sectors, each of said separate sectors being associated with a respective one of said magnetic poles, said rotor including an outer ring positioned about said rotor in a clamping relationship for holding said radially outer portions of said rotor in compression against said magnets. 
     
     
       10. The motor of claim 1 wherein said radially outer edges of each of said third and fourth permanent magnets are mitered, said third and fourth permanent magnets being positioned such that said mitered edges are parallel to a radius line of said rotor. 
     
     
       11. The motor of claim 10 wherein said mitered edges are abutting, said rotor comprising a radially inner portion coupled to a shaft of the motor and a radially outer portion, said magnets being positioned between said radially inner and outer portions of said rotor with said slots being defined by spaces between said radially inner and outer portions. 
     
     
       12. The motor of claim 1 wherein said slots extend radially outward beyond a respective one of said magnets inserted in each of said slots, and further including a nonmagnetic weldable insert positioned in each of the extended portions of said slots, said inserts being welded to said rotor along all contacting surfaces therebetween to form a composite rotor structure. 
     
     
       13. The motor of claim 12 wherein said inserts only partially fill said extended position of said slots, said inserts being welded in contact with predetermined sections of said rotor and leaving an air gap between other sections of said rotor and said insert for flux control. 
     
     
       14. The motor of claim 1 and including a plurality of apertures extending radially through said rotor, each of said apertures terminating in a threaded portion adjacent the motor shaft, a corresponding plurality of bolts inserted one each into said apertures and threadedly engaging said threaded portion for holding said rotor against radial deflection during operation. 
     
     
       15. The motor of claim 14 wherein said rotor comprises a plurality of stacked laminations positioned about a radially inner solid cylinder, said threaded portion of said apertures being formed in said cylinder. 
     
     
       16. The motor of claim 15 wherein preselected ones of said magnets are formed with grooves for passing said bolts therethrough. 
     
     
       17. The motor of claim 8 including a plurality of apertures extending radially through said rotor, each of said apertures terminating in a threaded portion adjacent the motor shaft, and a corresponding plurality of bolts inserted one each into said apertures and threadedly engaging said threaded portion for holding said rotor against radial deflection during operation. 
     
     
       18. The motor of claim 1 wherein each of said magnets is positioned within axially-directed slots having a radial length greater than the width of said magnets for creating an area of nonmagnetic characteristics adjacent an edge of said magnets for preventing magnetic short circuiting of said magnets. 
     
     
       19. A rotor assembly for an internal permanent magnet rotor comprising: a plurality of interior laminations stacked to form a substantially continuous internal core having a predetermined circumferential configuration defining a plurality of substantially planar land areas;   a plurality of permanent magnets positioned on the land areas of the internal core, the magnets being arranged in preselected groups for establishing a corresponding preselected number of magnetic poles, each of the preselected groups comprising a plurality of angularly-oriented magnets forming at least one substantially W-shaped arrangement;   a plurality of external laminations stacked to form a substantially continuous external core surrounding the internal core having a plurality of internal land areas for mating with external surfaces of each of the magnets when the external core is assembled onto the internal core and magnets; and   a circumferential band encompassing the external core for holding the external core in its assembled position on the internal core and magnets.   
     
     
       20. The rotor assembly of claim 19 wherein the external core comprises a plurality of core sectors, each of the core sectors corresponding to one of the magnetic poles, the circumferential band holding the core sectors in their respective assembled relationship on the internal core and magnets. 
     
     
       21. A rotor assembly for an internal permanent magnet rotor comprising; a plurality of interior laminations stacked to form a substantially continuous internal core having a predetermined circumferential configuration defining a plurality of substantially planar land area;   a plurality of permanent magnets positioned on the land areas of the internal core, the magnets being arranged in preselected groups for establishing a corresponding preselected number of magnetic poles, each of the preselected groups comprising a plurality of angularly-oriented magnets forming at least one substantially W-shaped arrangement;   a plurality of external laminations stacked to form a substantially continuous external core surrounding the internal core having a plurality of internal land areas for mating with external surfaces of each of the magnets when the external core is assembled onto the internal core and magnets; and   a plurality of lamination ligaments extending from each interior lamination to a corresponding one of the external laminations for coupling the internal core to the external core, the ligaments extending through circumferential spaces between adjacent ones of the magnets.   
     
     
       22. The rotor assembly of claim 21 wherein the magnets fit loosely in axially-extending slots defined by spacing between the internal and external cores and the connecting ligaments, the magnets being held in fixed positions within the slots by a potting compound inserted therein. 
     
     
       23. The rotor assembly of claim 22 wherein the potting compound comprises a relatively low melting point, nonmagnetic metal. 
     
     
       24. The rotor assembly of claim 23 including a plurality of axially-extending apertures through the internal and external cores adjacent preselected ones of the magnets, the apertures being filled with the potting compound for enhancing axial strength of the rotor assembly 
     
     
       25. The rotor assembly of claim 24 wherein at least some of the axially-extending apertures are coupled to the slots containing the magnets by passages therebetween. 
     
     
       26. The rotor assembly of claim 23 and further including a plurality of uniformly circumferentially-spaced, axially-extending apertures adjacent an outer circumference of the external core, each of the apertures being filled with the metal whereby the rotor assembly is adaptable for use in a line start motor. 
     
     
       27. A rotor assembly for an internal permanent magnet rotor comprising: a plurality of interior laminations stacked to form a substantially continuous internal core having a predetermined configuration defining a plurality of substantially planar land areas;   a plurality of permanent magnets positioned on the land areas of the internal core, the magnets being arranged in preselected groups for establishing a corresponding preselected number of magnetic poles, each of the preselected groups comprising a plurality of angularly-oriented magnets forming at least one substantially W-shaped arrangement;   a plurality of external laminations stacked to form a substantially continuous external core surrounding the internal core having a plurality of internal land areas for mating with external surfaces of each of the magnets when the external core is assembled onto the internal core and magnets;   a plurality of apertures formed radially through the external core and aligned with spaces between adjacent ones of the magnets;   a plurality of apertures formed in the internal core and terminating at a preselected inner radius in a threaded portion, the apertures in the internal core being aligned with the apertures in the external core; and   a plurality of bolts extending through the internal core apertures and threadedly engaging the threaded portion in the internal core for holding the external core in its assembled position in the internal core with the magnets therebetween.   
     
     
       28. The rotor assembly of claim 27 including a substantially solid inner cylinder within the interior laminations, the threaded portion of the apertures being formed in the inner cylinder. 
     
     
       29. A permanent magnet rotor for a dynamoelectric machine comprising: a core having a centerline axis and including a pair of generally opposite end faces, and an outer circumferential surface defined about the centerline axis and interposed between said opposite end faces; and   a set of magnetic poles defined in said core, each magnetic pole being defined between a pair of adjacent imaginary planes extending generally radially and in angular relation from the centerline axis and each magnetic pole including a pair of sets of permanent magnets extending generally axially of said core between said opposite end faces, at least two permanent magnets of one of said permanent magnet sets respectively having pole faces disposed at least adjacent the adjacent imaginary planes of said each magnetic pole and extending in generally parallel relation therewith, and at least another two permanent magnets of another of said permanent magnet sets being angularly oriented with respect to each other and spaced between said at least two permanent magnets of said one of said permanent magnet sets, said at least another two permanent magnets in their angular orientation being spaced closest together adjacent said outer circumferential surface.